FYI
From the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research
When this crack calves a new iceberg, it may take fifty percent of the floating existing glacial tongue with it. The ramifications for the biosphere could be immense.
Cracks in the floating ice tongue of Petermann Glacier in the far northwest reaches of Greenland indicate the pending loss of another large iceberg. As glaciologists from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) report in a new study, the glacier's flow rate has increased by an average of 10 percent since the calving event in 2012, during which time new cracks have also formed—a quite natural process. However, the experts' model simulations also show that, if these ice masses truly break off, Petermann Glacier's flow rate will likely accelerate further and transport more ice out to sea, with corresponding effects on the global sea level. The study was recently released in the Journal of Geophysical Research: Earth Surface and is freely available.
snip
Located in the outermost northwest corner of Greenland, Petermann Glacier is one of the most prominent glaciers in the region: partly because its catchment encompasses four percent of the Greenland Ice Sheet, and partly because it is one of only three glaciers in Greenland with a floating ice tongue. That tongue currently extends roughly 70 kilometres into Petermann Fjord. Cracks 12 kilometres above the previous glacier edge indicate that, in the near future, another major iceberg could calve from Petermann Glacier.
snip
The researchers subsequently simulated the glacier's observed ice transport in a computer model and were able to confirm that the loss of a large iceberg in August 2012 is what triggered the acceleration. "On their way to the sea, the glacier's ice masses rub along the rock walls that enclose the fjord to the left and right. If a major iceberg breaks away from the end of the glacier's tongue, it will reduce the tongue's overall length, and with it, the route along which the ice masses scrape against the stone. This in turn limits the walls' braking effect, so that the glacier begins flowing faster," explains AWI ice modeller and first author Martin Rückamp.
The computer model predicts that a new calving event would produce a similar acceleration. "We can't predict when Petermann Glacier will calve again, or whether a calving event would actually calve along the cracks we identified in the ice tongue," says Rückamp. "But we can safely assume that, if it does come to a new calving event, the tongue will retreat considerably, and the rock's stabilizing effect will further decline."
Jason Box, Greenland glaciologist, is interviewed by Bill Maher and discuss Petermann glacier back in 2014.
x xYouTube Video